Frost dates California San Jose

Frost dates in San Jose, California

Last spring frost Jan 2 First fall frost Dec 25 NOAA 1991-2020

The average last spring frost in San Jose is Jan 2 and the average first fall frost is Dec 25, measured at SAN JOSE, about 1 mile from the city centre. Below: how sure those dates are, and what to start, sow and set out each week.

Average last spring frostJan 232°F, 50% probability
Average first fall frostDec 2532°F, 50% probability
Days between them357average frost-free season
How sure is that date? NOAA probability levels for a 32°F freeze
ProbabilityFreeze still comes after (spring)First freeze has come by (fall)
90%Dec 14Jan 14
50%Jan 2Dec 25
10%Jan 23Dec 4

Read it like this: in half of years the last 32°F freeze of spring comes after Jan 2, and in 1 year in 10 there is still a freeze after Jan 23. In 1 year in 10 the first fall freeze arrives before Dec 4.

Measured at: SAN JOSE, CA (NOAA station USC00047821), about 1 mile away at 67 ft, 17 years of record in 1991-2020.

Other stations nearby, for comparison:

  • SAN JOSE, CA (NOAA station USW00023293), about 2 miles away at 51 ft, 21 years of record in 1991-2020: last spring frost Jan 12, first fall frost Dec 22
  • LOS GATOS, CA (NOAA station USC00045123), about 8 miles away at 365 ft, 24 years of record in 1991-2020: last spring frost Feb 2, first fall frost Dec 6

Seed-starting schedule for San Jose, CA

Counted from a last frost date of Jan 2 (the average: a freeze comes later than this in half of years).

  1. Week of Sep 2614 weeks before last frost
    • Start seeds indoorsLeekSep 26 to Oct 10
    • Start seeds indoorsOnionSep 26 to Oct 10
  2. Week of Oct 313 weeks before last frost
    • Start seeds indoorsParsleyOct 3 to Oct 10
  3. Week of Oct 1012 weeks before last frost
    • Start seeds indoorsCeleryOct 10 to Oct 24
    • Start seeds indoorsSpinachOct 10 to Oct 24
  4. Week of Oct 2410 weeks before last frost
    • Start seeds indoorsBroccoliOct 24 to Nov 7
    • Start seeds indoorsBrussels sproutOct 24 to Nov 7
    • Start seeds indoorsCabbageOct 24 to Nov 7
    • Start seeds indoorsKaleOct 24 to Nov 7
    • Start seeds indoorsKohlrabiOct 24 to Nov 7
  5. Week of Oct 319 weeks before last frost
    • Start seeds indoorsLettuceOct 31 to Nov 7
  6. Week of Nov 78 weeks before last frost
    • Start seeds indoorsCauliflowerNov 7 to Nov 21
    • Start seeds indoorsEggplantNov 7 to Nov 21
    • Start seeds indoorsPepperNov 7 to Nov 21
    • Start seeds indoorsSwiss chardNov 7 to Nov 21
  7. Week of Nov 147 weeks before last frost
    • Start seeds indoorsTomatoNov 14 to Nov 28
  8. Week of Nov 216 weeks before last frost
    • Start seeds indoorsBasilNov 21 to Dec 5
    • Set transplants outSpinachNov 21 to Dec 12
  9. Week of Dec 54 weeks before last frost
    • Sow seed outdoorsRadishDec 5 to Dec 19
    • Sow seed outdoorsSwiss chardfrom Dec 5
    • Sow seed outdoorsTurnipDec 5 to Dec 19
    • Set transplants outBroccoliDec 5 to Dec 19
    • Set transplants outBrussels sproutDec 5 to Dec 19
    • Set transplants outCabbagefrom Dec 5
    • Set transplants outKalefrom Dec 5
    • Set transplants outKohlrabifrom Dec 5
    • Set transplants outLeekfrom Dec 5
    • Set transplants outLettuceDec 5 to Dec 12
    • Set transplants outOnionfrom Dec 5
  10. Week of Dec 123 weeks before last frost
    • Start seeds indoorsCucumberDec 12 to Dec 19
    • Set transplants outParsleyDec 12 to Dec 19
  11. Week of Dec 192 weeks before last frost
    • Start seeds indoorsMelonDec 19 to Dec 26
    • Start seeds indoorsPumpkinDec 19 to Dec 26
    • Start seeds indoorsSummer squashDec 19 to Dec 26
    • Start seeds indoorsWinter squashDec 19 to Dec 26
    • Start seeds indoorsZucchiniDec 19 to Dec 26
    • Plant seed potatoes outdoorsPotatoDec 19 to Dec 26
    • Set transplants outCauliflowerfrom Dec 19
    • Set transplants outSwiss chardfrom Dec 19
  12. Week of Jan 2Last frost week
    • Sow seed outdoorsBeanfrom Jan 2
    • Sow seed outdoorsParsnipfrom Jan 2
    • Set transplants outCeleryfrom Jan 2
  13. Week of Jan 91 week after last frost
    • Plant slips outdoorsSweet potatoJan 9 to Jan 16
    • Set transplants outCucumberJan 9 to Jan 16
    • Set transplants outTomatoJan 9 to Jan 16
  14. Week of Jan 162 weeks after last frost
    • Set transplants outBasilfrom Jan 16
    • Set transplants outEggplantJan 16 to Jan 23
    • Set transplants outMelonfrom Jan 16
    • Set transplants outPepperfrom Jan 16
    • Set transplants outPumpkinfrom Jan 16
    • Set transplants outSummer squashfrom Jan 16
    • Set transplants outWinter squashfrom Jan 16
    • Set transplants outZucchinifrom Jan 16

Not in the city centre? Look up your own ZIP code

More in California

Where the numbers come from

Sources and method

Frost dates. U.S. Climate Normals 2020: U.S. Annual/Seasonal Climate Normals (1991-2020), NOAA National Centers for Environmental Information (Palecki, Durre, Applequist, Arguez and Lawrimore, 2021). These are 30-year station statistics for 1991 to 2020. "Frost" here means an air temperature of 32°F or lower at the station. We use 6,539 stations that have at least 10 years of record and a published date; 176 more are stations where a freeze is too rare for NOAA to date, and 180 are stations cold enough to have frost risk all year.

Probability level. The headline dates are NOAA's 50% level: in half of years the last spring freeze comes later than that date, and in half of years the first fall freeze comes earlier. The 10% and 90% levels are shown next to them. For tender plants, the 10% spring date is the safer one to plan from: a freeze follows it in only 1 year in 10.

Which station. Your ZIP code is matched to the nearest of those stations by straight-line distance from the ZIP code's centre point (GeoNames, geonames.org, CC BY 4.0; 40,979 ZIP codes in the 50 states and DC). Nearest is not always most alike: a station on a hill, in a valley or by the water can differ from your garden by a week or more. That is why the station's name, distance and elevation are shown with every result, along with two more stations nearby. NOAA makes the same point: the normals are limited between stations as distance grows horizontally and vertically.

Seed-starting offsets. Growing Vegetables: When to Plant Your Vegetable Garden, a fact sheet from University of New Hampshire Extension. It gives each crop's weeks from seed to transplant and when it is safe to set out or sow relative to the last frost. The method is theirs too: take the planting date and count back the seed-to-transplant weeks. Where the fact sheet gives a range of planting dates, the start-indoors dates count back from the earliest one. The figures used, as the fact sheet states them:

  • Basil: Seed to transplant 6-8 weeks; set out 2 weeks after last frost.
  • Bean: Plant seed in garden after last frost.
  • Broccoli: Seed to transplant 4-6 weeks; set out 2-4 weeks before last frost.
  • Brussels sprout: Seed to transplant 4-6 weeks; set out 2-4 weeks before last frost.
  • Cabbage: Seed to transplant 4-6 weeks; set out 4 weeks before last frost.
  • Cauliflower: Seed to transplant 4-6 weeks; set out 2 weeks before last frost.
  • Celery: Seed to transplant 10-12 weeks; set out after last frost.
  • Cucumber: Seed to transplant 3-4 weeks; set out 1-2 weeks after last frost.
  • Eggplant: Seed to transplant 8-10 weeks; set out 2-3 weeks after last frost.
  • Kale: Seed to transplant 4-6 weeks; set out 4 weeks before last frost.
  • Kohlrabi: Seed to transplant 4-6 weeks; set out 4 weeks before last frost.
  • Leek: Seed to transplant 8-10 weeks; set out 4 weeks before last frost.
  • Lettuce: Seed to transplant 4-5 weeks; set out 3-4 weeks before last frost.
  • Melon: Seed to transplant 3-4 weeks; set out 2 weeks after last frost.
  • Onion: Seed to transplant 8-10 weeks; set out 4 weeks before last frost.
  • Parsley: Seed to transplant 9-10 weeks; set out 2-3 weeks before last frost.
  • Parsnip: Plant seed in garden after last frost.
  • Pepper: Seed to transplant 8-10 weeks; set out 2 weeks after last frost.
  • Potato: Plant seed potatoes in garden 1-2 weeks before last frost.
  • Pumpkin: Seed to transplant 3-4 weeks; set out 2 weeks after last frost.
  • Radish: Plant seed in garden 2-4 weeks before last frost.
  • Spinach: Seed to transplant 4-6 weeks; set out 3-6 weeks before last frost.
  • Summer squash: Seed to transplant 3-4 weeks; set out 2 weeks after last frost.
  • Sweet potato: Plant slips in garden 1-2 weeks after last frost.
  • Swiss chard: Seed to transplant 4-6 weeks; set out 2 weeks before last frost; or plant seed in garden 4 weeks before last frost.
  • Tomato: Seed to transplant 6-8 weeks; set out 1-2 weeks after last frost.
  • Turnip: Plant seed in garden 2-4 weeks before last frost.
  • Winter squash: Seed to transplant 3-4 weeks; set out 2 weeks after last frost.
  • Zucchini: Seed to transplant 3-4 weeks; set out 2 weeks after last frost.

Not on the calendar. The same fact sheet times these by soil temperature, not by frost date, so they get no date here:

  • Pea: as soon as the soil thaws.
  • Beet: when the soil warms to 45°F.
  • Carrot: when the soil warms to 60°F.
  • Corn: when the soil warms to 60°F.
  • Cucumber, pumpkin, summer squash, winter squash, zucchini: direct-sow when the soil warms to 70°F.

Rutabaga is left out: the fact sheet gives it New Hampshire calendar dates, not a frost offset.

The fact sheet was written for New Hampshire. The offsets are relative to the last frost, so they carry to other places with a spring frost, but where winters are mild many cool-season crops are grown in fall and winter instead. Your state's extension service has the local calendar. Dates are 30-year statistics, not a forecast: check the forecast before setting tender plants out.

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